<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
<script type="text/javascript">
    const users = {
        Alex: {
            email: 'alex@alex.com',
            skills: ['HTML', 'CSS', 'JavaScript'],
            age: 20,
            isLoggedIn: false,
            points: 30
        },
        Asab: {
            email: 'asab@asab.com',
            skills: ['HTML', 'CSS', 'JavaScript', 'Redux', 'MongoDB', 'Express', 'React', 'Node'],
            age: 25,
            isLoggedIn: false,
            points: 50
        },
        Brook: {
            email: 'daniel@daniel.com',
            skills: ['HTML', 'CSS', 'JavaScript', 'React', 'Redux'],
            age: 30,
            isLoggedIn: true,
            points: 50
        },
        Daniel: {
            email: 'daniel@alex.com',
            skills: ['HTML', 'CSS', 'JavaScript', 'Python'],
            age: 20,
            isLoggedIn: false,
            points: 40
        },
        John: {
            email: 'john@john.com',
            skills: ['HTML', 'CSS', 'JavaScript', 'React', 'Redux', 'Node.js'],
            age: 20,
            isLoggedIn: true,
            points: 50
        },
        Thomas: {
            email: 'thomas@thomas.com',
            skills: ['HTML', 'CSS', 'JavaScript', 'React'],
            age: 20,
            isLoggedIn: false,
            points: 40
        },
        Paul: {
            email: 'paul@paul.com',
            skills: ['HTML', 'CSS', 'JavaScript', 'MongoDB', 'Express', 'React', 'Node'],
            age: 20,
            isLoggedIn: false,
            points: 40
        }
    }

    //统计在线人数 
    const keysArr = Object.keys(users)  //字符串.
    var count = 0
    keysArr.forEach(
        function (item) {
            users[item].isLoggedIn == true ? count++ : count

        }
    )
    console.log(count);



    // 2.统计分数大于50的人数
    var c = 0;
    keysArr.forEach(
        (item) => users[item].points>50?++c:c
    )
    console.log(c);
    // 3.查找会MongoDB的人，并打印其名字
    keysArr.forEach(
        (item)=>{

            let  isAble = false;
            users[item].skills.forEach(
              (item)=>{
                if(item=="MongoDB"){
                    isAble=true;
                    
                }
              }

            )
            if( isAble){
                console.log(item);
            }
            

        }
    )
    // 4.查找同时会：MongoDB， Express，React，和Node 的人，并打印其名字
    keysArr.forEach(
        
        (item) =>{
            let c=0;
            users[item].skills.forEach(
                
                (item)=>{
                if(item=="MongoDB"||item=="Express"||item=="React"||item=="Node"){
                    c++;

                }
                }
            )
            if(c==4){
                console.log(item);
            }

        }
    )
</script>
</body>
</html>